Fine regulation on hour-glass like spongy structure of polyphenylsulfone (PPSU)/sulfonated polysulfone (SPSf) microfiltration membranes via a vapor-liquid induced phase separation (V-LIPS) technique

The fine micro-structure regulation of polymeric membranes is crucial to the separation performances. Herein, we prepared a novel Polyphenylsulfone (PPSU)/sulfonated polysulfone (SPSf) microfiltration membrane with ‘hour-glass’ like spongy micropore-structure via vapor and liquid induced phase separation (V-LIPS) technique. A precritical casting solution was prepared by adding a certain amount of H2O using N, N-dimethylacetamide (DMAc) as the solvent and Polyvinyl Pyrrolidone (PVP) as the pore-forming agent. The effect of residence time in vapor on membrane structures is extensively evaluated. Results revealed that the resultant membranes evolved from finger-like to bicontinuous structure with extending the exposure time (>5s) in vapor. The pure water flux of the membrane with the vapor time (30s) under the pressure of 0.2 bar reached a high value of 3045.7 ± 42.7 L/(m2∙h). Moreover, the obtained membrane M3 showed excellent separation properties for surfactant-stabilized n-hexane-in-water, isooctane-in-water and decamethylcyclopentasiloxane (D5)-in-water emulsions with rejection coefficient up to >99%, >99% and >98% and high rejection of 99.0% to SiO2 nanoparticles. Therefore, PPSU/SPSf membrane with controlled ‘hour-glass’ like spongy micro-pore structure showed high permeability with high rejection coefficient for both inorganic nanoparticles and oily water.